addfc38672c73efd5c4e559a2e455b086e3e20c5 causes boot issues with arm64 defconfig #649
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Upstream discussion: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html |
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Not an outright fix, but today I worked on improving LLVM's verification of the IR representation of asm goto so that we should be able to catch this kind of invalidated invariant easier in the future. It should also simply finding the bad transform: https://reviews.llvm.org/D67196 |
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upstream bug filed: https://bugs.llvm.org/show_bug.cgi?id=43222 |
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Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 llvm-svn: 371262
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Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371262 91177308-0d34-0410-b5e6-96231b3b80d8
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Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252
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Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252
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Fixed: https://reviews.llvm.org/rL371262 Now to make sure we get it in the clang-9 release (cc @zmodem) |
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Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371262 91177308-0d34-0410-b5e6-96231b3b80d8
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------------------------------------------------------------------------ r371262 | nickdesaulniers | 2019-09-06 23:50:11 +0200 (Fri, 06 Sep 2019) | 45 lines [IR] CallBrInst: scan+update arg list when indirect dest list changes Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 ------------------------------------------------------------------------ llvm-svn: 371376
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I've merged the commit to release_90 and replied on https://bugs.llvm.org/show_bug.cgi?id=43222 with the details. |
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------------------------------------------------------------------------ r371262 | nickdesaulniers | 2019-09-06 23:50:11 +0200 (Fri, 06 Sep 2019) | 45 lines [IR] CallBrInst: scan+update arg list when indirect dest list changes Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_90@371376 91177308-0d34-0410-b5e6-96231b3b80d8
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Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371262 91177308-0d34-0410-b5e6-96231b3b80d8
earl
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Summary: The list of indirect labels should ALWAYS have their blockaddresses as argument operands to the callbr (but not necessarily the other way around). Add an invariant that checks this. The verifier catches a bad test case that was added recently in r368478. I think that was a simple mistake, and the test was made less strict in regards to the precise addresses (as those weren't specifically the point of the test). This invariant will be used to find a reported bug. Link: https://www.spinics.net/lists/arm-kernel/msg753473.html Link: ClangBuiltLinux/linux#649 Reviewers: craig.topper, void, chandlerc Reviewed By: void Subscribers: ychen, lebedev.ri, javed.absar, kristof.beyls, hiraditya, llvm-commits, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67196 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@372923 91177308-0d34-0410-b5e6-96231b3b80d8
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Summary: The list of indirect labels should ALWAYS have their blockaddresses as argument operands to the callbr (but not necessarily the other way around). Add an invariant that checks this. The verifier catches a bad test case that was added recently in r368478. I think that was a simple mistake, and the test was made less strict in regards to the precise addresses (as those weren't specifically the point of the test). This invariant will be used to find a reported bug. Link: https://www.spinics.net/lists/arm-kernel/msg753473.html Link: ClangBuiltLinux/linux#649 Reviewers: craig.topper, void, chandlerc Reviewed By: void Subscribers: ychen, lebedev.ri, javed.absar, kristof.beyls, hiraditya, llvm-commits, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67196 llvm-svn: 372923
dtzWill
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Summary: The list of indirect labels should ALWAYS have their blockaddresses as argument operands to the callbr (but not necessarily the other way around). Add an invariant that checks this. The verifier catches a bad test case that was added recently in r368478. I think that was a simple mistake, and the test was made less strict in regards to the precise addresses (as those weren't specifically the point of the test). This invariant will be used to find a reported bug. Link: https://www.spinics.net/lists/arm-kernel/msg753473.html Link: ClangBuiltLinux/linux#649 Reviewers: craig.topper, void, chandlerc Reviewed By: void Subscribers: ychen, lebedev.ri, javed.absar, kristof.beyls, hiraditya, llvm-commits, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67196 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@372923 91177308-0d34-0410-b5e6-96231b3b80d8
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Summary: The list of indirect labels should ALWAYS have their blockaddresses as argument operands to the callbr (but not necessarily the other way around). Add an invariant that checks this. The verifier catches a bad test case that was added recently in r368478. I think that was a simple mistake, and the test was made less strict in regards to the precise addresses (as those weren't specifically the point of the test). This invariant will be used to find a reported bug. Link: https://www.spinics.net/lists/arm-kernel/msg753473.html Link: ClangBuiltLinux/linux#649 Reviewers: craig.topper, void, chandlerc Reviewed By: void Subscribers: ychen, lebedev.ri, javed.absar, kristof.beyls, hiraditya, llvm-commits, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67196
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Summary: The list of indirect labels should ALWAYS have their blockaddresses as argument operands to the callbr (but not necessarily the other way around). Add an invariant that checks this. The verifier catches a bad test case that was added recently in r368478. I think that was a simple mistake, and the test was made less strict in regards to the precise addresses (as those weren't specifically the point of the test). This invariant will be used to find a reported bug. Link: https://www.spinics.net/lists/arm-kernel/msg753473.html Link: ClangBuiltLinux/linux#649 Reviewers: craig.topper, void, chandlerc Reviewed By: void Subscribers: ychen, lebedev.ri, javed.absar, kristof.beyls, hiraditya, llvm-commits, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67196
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Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 llvm-svn: 371262
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Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371262 91177308-0d34-0410-b5e6-96231b3b80d8
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Summary: The list of indirect labels should ALWAYS have their blockaddresses as argument operands to the callbr (but not necessarily the other way around). Add an invariant that checks this. The verifier catches a bad test case that was added recently in r368478. I think that was a simple mistake, and the test was made less strict in regards to the precise addresses (as those weren't specifically the point of the test). This invariant will be used to find a reported bug. Link: https://www.spinics.net/lists/arm-kernel/msg753473.html Link: ClangBuiltLinux/linux#649 Reviewers: craig.topper, void, chandlerc Reviewed By: void Subscribers: ychen, lebedev.ri, javed.absar, kristof.beyls, hiraditya, llvm-commits, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67196 llvm-svn: 372923
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…st changes Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 llvm-svn: 371262 (cherry picked from commit 7a7bba2) Change-Id: If0be070043c54384cb7aa5fd5dd22224ede4dacf
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…st changes Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 llvm-svn: 371262 (cherry picked from commit 7a7bba2) Change-Id: I3d3a3dcf92c148e4e57653ea086c2febddbc4e38
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Oct 12, 2020
Summary: There's an unspoken invariant of callbr that the list of BlockAddress Constants in the "function args" list match the BasicBlocks in the "other labels" list. (This invariant is being added to the LangRef in https://reviews.llvm.org/D67196). When modifying the any of the indirect destinations of a callbr instruction (possible jump targets), we need to update the function arguments if the argument is a BlockAddress whose BasicBlock refers to the indirect destination BasicBlock being replaced. Otherwise, many transforms that modify successors will end up violating that invariant. A recent change to the arm64 Linux kernel exposed this bug, which prevents the kernel from booting. I considered maintaining a mapping from indirect destination BasicBlock to argument operand BlockAddress, but this ends up being a one to potentially many (though usually one) mapping. Also, the list of arguments to a function (or more typically inline assembly) ends up being less than 10. The implementation is significantly simpler to just rescan the full list of arguments. Because of the one to potentially many relationship, the full arg list must be scanned (we can't stop at the first instance). Thanks to the following folks that reported the issue and helped debug it: * Nathan Chancellor * Will Deacon * Andrew Murray * Craig Topper Link: https://bugs.llvm.org/show_bug.cgi?id=43222 Link: ClangBuiltLinux/linux#649 Link: https://lists.infradead.org/pipermail/linux-arm-kernel/2019-September/678330.html Reviewers: craig.topper, chandlerc Reviewed By: craig.topper Subscribers: void, javed.absar, kristof.beyls, hiraditya, llvm-commits, nathanchance, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67252 llvm-svn: 371262
JohnHolmesII
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Oct 12, 2020
Summary: The list of indirect labels should ALWAYS have their blockaddresses as argument operands to the callbr (but not necessarily the other way around). Add an invariant that checks this. The verifier catches a bad test case that was added recently in r368478. I think that was a simple mistake, and the test was made less strict in regards to the precise addresses (as those weren't specifically the point of the test). This invariant will be used to find a reported bug. Link: https://www.spinics.net/lists/arm-kernel/msg753473.html Link: ClangBuiltLinux/linux#649 Reviewers: craig.topper, void, chandlerc Reviewed By: void Subscribers: ychen, lebedev.ri, javed.absar, kristof.beyls, hiraditya, llvm-commits, srhines Tags: #llvm Differential Revision: https://reviews.llvm.org/D67196 llvm-svn: 372923
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https://git.kernel.org/next/linux-next/c/addfc38672c73efd5c4e559a2e455b086e3e20c5
The boot just hangs: https://travis-ci.com/ClangBuiltLinux/continuous-integration/jobs/229812606
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